how to wean bubs from nipple shields

Have you tried lying down with him in bed and offering the breast while he is sleepy?
Maybe place the shield in his mouth and allow him to root for the breast, then quickly take the shield off and latch him directly on the breast?

I have 6 month old twins and have been using nipple shields since they were born.
The advice I got was to start with once feed a day without a nipple shield. Once that was established to move to another feed.
Also what was suggested was to start the feed with the nipple shield but once the nipple had come out fully, to remove the nipple shield mid feed.

I never ended up weaning them though as Aoife would have been more difficult to wean and they seem to be coping pretty well with them.

Emily is 5 months old now. She was born 2 months prem and I had to start bf with a nipple shield when she was 2 weeks old. I started trying the odd feed without the shield from 1 month old and increased the frequency of feeds without the shield gradually until she was 2 and a half months old. I would mix it up by starting feeds without it which would last only a few minutes before she pulled away and I had finish the feed using the shield, and sometimes would try without the shield halfway through the feed. Eventually she got used to the idea and decided herself when she preferred feeds without the shield. I found that the shield became more of a nuisance to her when she would push it away with her mouth or hands and milk would leak from the bottom of the shield anyway when she did this. It took a lot of weeks of patience and persistence but if you just keep trying, but not pushing him too hard, eventually he might decide when he's ready to feed without the shield. Hope it all goes well for you and good luck!